Part A: A: the bankers hasty thoughtless actions lead to trouble and despair for him.
Part B: B: “desperate gambling on the stock exchange, wild speculation and the excitability which he could not get over even in advancing years, had by degrees led to the decline of his fortune and the proud, fearless, self-confident millionaire has become a banker of middling rank, trembling at every rise and fall in his investments”
In Part A, A is the correct answer because the banker is constantly taking making quick decisions with his money. We see this in the supporting evidence of option B. It describes his gambling as desperate and him making decisions based on "wild speculation". We see the despair further on in the story when it says, "When he got home he lay on his bed, but his tears and emotion kept him for hours from sleeping.”
